1. Field of the Invention
The present invention relates to a manufacturing method of a master disk used for manufacturing an optical disk which is an optical recording/reproducing medium, and to the master disk.
2. Description of the Related Art
In general, a high density optical disk such as a digital versatile disk (DVD)--random access memory (RAM) includes grooves 1 and lands 2 where information is recorded along spiral tracks, as shown in FIG. 1. Pits 3 are formed on the grooves 1 and the lands 2, respectively, to thereby record desired information thereon. Since both the grooves 1 and the lands 2 are used, a larger amount of information can be recorded with high density as compared to a conventional optical disk in which information is recorded either on the groove 1 or the land 2.
The optical disk is manufactured through processes as shown in FIGS. 2A through 2D. As shown in FIG. 2A, a photoresist 20 is coated on a substrate 10, and then the photoresist 20 is exposed according to patterns of the groove 1, the land 2 and the pit 3 by simultaneously radiating a laser 30 for a groove and a laser 30' for a pit on a surface of the photoresist 20 while rotating the substrate 10. Reference numerals 31 and 31' indicate modulators for turning on/off the lasers 30 and 30', respectively.
Subsequently, as shown in FIG. 2B, an etching reagent E is sprayed on the exposed substrate 10, to thereby manufacture a master disk 15 where grooves, lands and pits are formed.
The master disk 15 is stamped to manufacture a father stamper 25 as shown in FIG. 2C, and then an optical disk is copied by an injection molding method in which resin 35 is injected into a mold 40 having the father stamper 25 mounted thereon, as shown in FIG. 2D.
In the above method, since the patterns of the lands, the grooves and the pits are formed on one photoresist layer through exposure and then simultaneously etched, boundaries between the land, the groove and the pit are not sharp. Accordingly, start and end points of information signals are not detected with accuracy during the reproduction of the information of the optical disk, thereby increasing jitter errors in which an output signal is not generated on time.